The invention is based on a priority application EP 04 293 125.3 which is hereby incorporated by reference.
The invention relates to a method for providing a trusted feedback in an access network according to the specifying features of claim 1, plus an access network according to the specifying features of claim 6, plus an access multiplexer according to the specifying features of Claim 10.
Today, the Internet Protocol IP is becoming the unified network layer for transporting all sorts of services such as voice & video traffic. Typically, these services are very delay and/or jitter sensitive and the quality of the transported service will very much degrade by e.g. packet loss somewhere inside the network.
When transporting these services over an access network, the operator might require real time monitoring of the quality of the transported service associated with a dynamic feedback.
This dynamic feedback could be used e.g. by the source of the transport stream in order to change e.g. the compression and/or codec bit rate, or it could be used by the network operator's infrastructure to generate troubleshooting alerts, or by the billing system in order to give a reduction on the price for the service, e.g. when a Pay Per Use model is used for the service. The source can be e.g. a video server for video streaming, or a session border controller for voice services.
Today access multiplexer like Digital Subscriber Line Access Multiplexer, DSLAM, have some features available to monitor the traffic, however, these are overall statistics: e.g. overall packet loss inside the switch or packet loss inside a buffer of a line card, amount of bad checksums of packets on a certain PVC, etc. Moreover, these statistics are not specific to a certain service and not real-time at all. Their primary goal is to provide the network management on a daily, weekly or monthly basis with data for measuring the health of e.g. an access line. The data are transmitted via e.g. the Simple Network Management Protocol, SNMP.
The drawback of this proceeding is that the monitoring capabilities in today's DSLAMs are too general and deal with very node specific information that are not scheduled to be read on a per session basis. Furthermore the information is useless for end-to-end service monitoring, since it is node specific.
For real-time service monitoring, some features are available inside the transport layer for real time IP services. The Real Time Protocol, RTP, is typically used for transporting these services on UDP/IP (User Datagram Protocol). RTP also contains a protocol, called the Real Time Control Protocol, RTCP, which very frequently, e.g., every few seconds, delivers sender- and receiver-reports comprising a feedback about the end-to-end, i.e. server to user quality of the real-time service regarding packet loss, jitter and delay.
Today, most of the real time transport migrates towards the RTP protocol. Some older technologies have however proprietary mechanism that includes most of the RTP transport features, though often without control protocol. The most known example is e.g. MPEG2_TS video transport over UDP and/or IP. This video encapsulation contains all RTP features. If service feedback is needed, a dedicated feedback protocol other than RTCP is typically required to monitor on the fly the health of the service.